Fluid coking process with quenching of hydrocarbon vapors



c. E. JAHNIG May 7, 1957 FLUID COKING PROCESS WITH QUENCHING OFHYDROCARBON VAPORS Filed Dec. 30, 1953 2 Sheets-Sheet 1 H lGH-T EMPERATURE VAPORS FIG.|

QUENCH "coKER PRODUCT VAPORS INVENTOR CHARLES E JAH NIG FIG.3

LIQUID QUENCH ATTO RN EY C. E. JAHNIG May 7, 1957 FLUID COKING PROCESSWITH QUENCHING OF HYDROCARBON VAPORS Filed Dec. 30, 1953 2 Sheets-Sheet2 I-EATING m U m L FLUID COKING BED R KL

A OE

CL CS I S STEAM Charles E. Jahnig Q Inventor FLUID CQKIN G :PROCESS WITHQUENCHING- OF HYDROCARBON VAPORS Charles EiJahnig; RedBank; N. J.-,assignor to Esso Re- Search anWEhgineefing- Company; a corporationotDelaware Application December 30, 1953, Serial No. 401,305 Z'CI'tli'IiIS-Q (Cla19655) This invention relates generally" to thetransporting and coolingof hot hydrocarbongases' having atendency to'forrn coke deposit-son the conduits and equipment containing them; hlore-particularly it relates to methods and means for "transporting andcooling of the hot prod uct; 'gas'es'fr'oni fluid coking operations:

The-fluid coking process for heavy hydrocarbons has reee'ntl ybeenproposed; oil'sare' upgraded by this cokingproce'ss, utilizing thefiilidiza'tion' technique, to'lighter', more valuableprodu'cts byinjecting the'oil's into a reactor vessel containing a bed of hot'fihely dividedfluidized solidsv Pyrolysis of th'e' oil occurs' inthevessel and carbonaceous residue is -depos'ited on the fluidized solids"and lighter gasiform' hydroe'areons are' -evc'alv'edand withdrawn asproduct. The-"reaction temperature ofthe bed'is maintainedbycontinuously"withdrawinga portion of i the" carh'omconta'ini'ng: solidsand circul'atingthem to an external heater and' bac 1 One oftheprohlemsin fluid coking. is 'the'b'uilding up ofi coke deposits in-th'e systemthat handles 'the product hydrocarbon gases beforethey are'cool'ed belowa critical cokihg=temperature;'i. e., below-700"F; Somewof'thehydrocarbons-in the coker overhead" vapors are' high boiling and Willreadilycondense. If condensation occurs-inn critical coking range ofabout"700"" 1000 R, the condensate" c'okes, causing fouling and pluggingof the-equi'pment So long asthe gases rem'ai'n' above the crit i'cal"temperature range; coking will not occur. Bus in cooling thegases;coking will occur while the gases pas's' through this range-if" there"are attendant sunfaces' for the 'coke to form on:

This problern is aggravated somewhat by the fact that thehydrocarbons-in 'this 'overhead productare reactive andmiay te'nd topolymerize. In"this'"way, molecular weight is -raiised and ga'se's}which at first were-at or above their dew point; areconverted to"am'ixtu're 'of part liquid-'and vapor which can condense and cause" cokeformations? Particularly trouhl'esomeplaces where" this coking occmsisin the roducttransfr lines fronr'the-fliiid coking reactionwessel totire uenching (or fractionat'ing) zone and-at the nozzle introducing thevapors info thequench zone.

One method of caring for this difficulty is to add a volumeof"superheated" steam'or other" light" inert gas to the reactor 'outl'etproducts to dilute them. This operates to lower the dew point of thegaseous mixture thereby inhibiting.condensation. This, -howev'er, iscostly and leads togreater expense in the recovery of products. 1

This -invention is based upon the 'discoverythat coke epositsby': thegases can. be attributed 'to surfacetemperatures in' af criticalurangewI-fa surface is above the dew point temperature of the gases,condensation and, consequently, coking does not occur. If thetemperature is about 600 F, or less, the reaction rate is slow enough sothat serious coke deposits do not form. Within a Biiefly stated,hydrocarbon Patented May 7, 1957 2, cri t-ical sufface temperature rangeof about 700-l000- Fa; there is condensation and sufiicient coking tobuild up a deposit.-

Aceordingly, anobject of this invention is to prevent coking-and'foulihgof equipment containing high temperature hydrocarbon vapors. Amore specific object is to'pr event carbon'deposition by hot'hydrocarhongases on the surfaces ofconfining vessels and conduits by judiciouscontrol of surface temperatures. Anotherohje'c-t is to provide a-methodfor cooling hothydrocarbon vapors' to a-temperat'ure below acriticalcoking temperature without the accompanying formation of coke deposits.-Other objects and advantageswill appear more clearly as the attacheddrawings, forming a part of this specification; are discussed" indetail.

Generally stated; the objects ofthis invention are attained in a systemhandling high temperature hydrocarbon v'a'pors -from a reactor bymaintaining the temperatur e' of confiiiing surfaces ahove the dew pointof the vapors prior to" quenching the vapors, so that condensationiandcoking in the liquid phase is avoided; quenohing-r thevapors fr'om -thereaction temperature to about 700-7'5'0 F., in such a manner that thetransition through. the critical coke deposition range is in the vaporphas'e'; and thereafter maintaining the temperaturerofi confiningsurfaces below-about 700 F. Preferably, the surfaces of equipmentimmediately following the quenching" zone are washed with liquid;

This inventionis concernedwitha novel quenchnozzle depicted i-nthe'attacheddrawings, and its use-in such a manner" that problems of'coke deposition by high temperature hydrocarbon' vapors are avoided;

m the drawings;

Figure 1 depicts -in cross-seetiom'a'nozzle arrangement constructedaccordin'g' to :the principle of this invention. The; nozzle is used 'tohorizont'ally introduce high-tent perature vaporsinto a 'scrubbing 'or'fracti onatin'gzone:

Figure 2 illustratesanother arrangement for intro ducingrjhot gases intoa quench zone.

Figure-3 portraysua conventional quenching arrangem'ent' andwill beusedto emphasize the advantagesof the *arrangement of Figure 2.

Figure 4 illustrates the use of this invention in 'a hydrocarbon: oil-:fluid coking.- process.

lnwFi'gure -"l; thef-hot hydrocarbon gases are being transported by;:pipe 2. All surfaces of the equipment i n co'n-' tact with thevgases-priorto' this point are to be unders'tood to' have beenmaintained' at a temperature above about 900 to=1000t F:

Itis to -be 'understood: that the critical temperature will vary'zwithspecific processe's. For example; the dew' point orconden'sation point05 gases fro'm a-fluid 'c'oker' 'operafl ing at a temperature ofiabout950 FL; will be *about'QSO F'- For -a :coker operatingzat' aternperature 'of 900 'Fztlie dew point will be about 900"F;- It issuflicient to keep surface temperatures above this dew" point. Heatingmeans '6 is depicted for keeping Ithe" surface of pipe- '2 above thedew-point of the gases' Astearn coil wrapped aroundthe-pipe -isthepreferred mode 'ofi'hea-t'ing; although other meanscanbe used suohas an'electric-heat ing-, elem'ent. Insulation can be used to 'help maintainthe desiredtemperature: For example; the ""outs'ide of theheating-coil 601' "the inside Of! pipe 7*can be=insuiatedi Pipe 2 enters acoolingzonewhich ca'nbe a'fraetionat ing tower, quenchtank, scrubbing-toweror thelike; The gases issue from the pipe and areimmediately mixed-with adowncomingl coolant and cooled in the vapor phase: This coolanfnormallywill be a liquid such as water or reflux in a fractionating column inthe form of a spray, stream or droplets. However, the cooling can beaccomplished by finely divided solid material or by a stream of cool gassuch as steam. Suitable solid coolants are shot having about ,6 inchdiameter or coke from a fluid coking operation.

For purposes of illustration, the cooling zone is shown as beingcontained in a vessel 1 with an entrance port constructed of a pipe 5and flange 4. A flange 3 is aflixed to pipe 2 and matches flange 4. Theflanges are held together, with suitable gasketing between them, bybolts (not shown) in holes 9. In this manner, the pipe can be mounted onthe vessel 1.

An interior concentric balfle 7 is arranged over the protruding pipe toprotect it and the heating means from the coolant. Bleed gas, such assteam, is admitted by line 8 to the annulus formed by the baflle toprevent gases from entering the annulus, due to any surges in thesystem, and coking.

While the pipe 2 is kept hot, the baflle and the walls of the vessel arekept at a temperature below 700 F. by the coolant so that coke will notform on them. Thus, it can be seen that by this invention, when producthydrocarbon vapors are in a critical coking temperature range, which fora fluid coking vessel is about 780-900 F., there are no equipmentsurfaces present at this temperature upon which carbon deposition canform. In cases where it is necessary to have a surface temperature inthis temperature range, the surface can be blanketed with a purge gas,e. g., steam, as was done to protect zone A of Figure 1.

In Figure 2, a line quench arrangement for the gases is shown. Hotvapors are introduced downwardly into the quench chamber 13 by pipe 11which protrudes inwardly into the chamber. The pipe 11 is kept at a hightemperature by a steam heating coil 12. A spray ring 14, supplied with aliquid coolant by line 15, is mounted just below the end of pipe 11. Thegases upon emerging from the pipe are immediately cooled below theircoking forming temperature by the liquid quench.

Again, although it is not mandatory, bleed gas is admitted by line 16 tothe space around the pipe to prevent hot gases and coolant from surgingupwardly and contacting the heating means. Line 17 removes the cooledgases from the quench tank and they are then carried to furtherprocessing such as a separation step.

Figure 3 illustrates a conventional method of quenching high temperatureproduct gases from a coker. In the drawing the vapors are being conveyedby line 22 which is heated by element 23 and are cooled by a liquidsupplied by line 24. It has been found that an area, B, adjacent to thecoolant inlet port has a temperature within the dewpoint of the vapors,even though the pipe is heated up to to this point. Consequently cokedeposits build up at this point. Also, on the side of the pipe, C,opposite from the quench port, deposits build up'because the swirlingand erratic motion of the liquid and vapors leaves an area having acritical temperature. In the nozzle arrangement of Figure 2, the coolingof the vapors occurs in the vapor phase. The interior walls 18 of thequench chamber 13 are further protected by a liquid film. If theswirling vapors do contact thewall, carbon deposition is prevented bythe liquid film.

Thus it can be seen that by the method of this invention, hightemperature gases can be effectively cooled without the accompanyingformation of coke deposits.

Figure 4 shows the quenching arrangement of this invention as used tohandle vapors produced by a hydrocarbon oil fluid coking process. Asshown, fluid coking vessel 30 contains a fluid coking bed 32 fluidizedby steam supplied by line 29. The coking bed 32 is maintained at acoking temperature. A hydrocarbon oil is injected into the coking bed byline 31. Upon contact with the heated finely divided solids, the oilundergoes vaporization and pyrolysis, depositing coke residue on thesolids. Vapors 4 are removed overhead from the coking zone throughcyclone 35, and then passed by line 36 to a vapor cooling vessel 40.

According to this invention, line 36 is heated by heating elements 37.The terminal portion of line 36 projecting into vessel 40 is protectedby a cylindrical concentric batfle 38. Bleed gas is admitted by line 39into the annular passageway formed by this cylindrical baflle. Liquidcoolant supplied by line 41 is sprayed into the vapors issuing from line36. Cooled vapors are removed from the upper portion of vessel 40 byline 42 and the liquid coolant, along with any condensed material, isremoved by line 43 from the bottom portion of vessel 40.

What is claimed is:

1. In a hydrocarbon oil fluid coking process wherein high temperaturehydrocarbon vapors are produced in a coking zone and said hydrocarbonvapors have a propensity to form coke deposits on attendant surfaces, amethod of preventing said coke deposits while cooling said hydrocarbonvapors through a critical coke deposition temperature range whichcomprises withdrawing said hydrocarbon vapors from said coking zonethrough a gas impervious passageway, maintaining the interior surfacetemperature of said passageway above the dew point of said hydrocarbonvapors by means of heating elements, injecting said hydrocarbon vaporsfrom said passageway into a gas cooling zone at an interior pointremoved from the confines of said gas cooling zone, forming a secondpassageway in said cooling zone about said gas impervious passageway andheating elements extending into said cooling zone, said secondpassageway terminating and opening into said gas cooling zone at thepoint of termination of said gas impervious passageway, maintaining theouter confines of said passageway below 780 F., injecting a bleed gasinto said second passageway to prevent entrance of hydrocarbon vaporsthereto, cooling said vapors below 780 F. in the vapor phase throughcontact with a finely divided liquid coolant, and withdrawing cooledvapors from said cooling zone.

2. In hydrocarbon oil fluid coking system comprising a reactor vessel, acoking bed of finely divided fluidized solids therein, and a vaporcooling vessel, the improvement comprising a gas impervious cylindricalconduit extending from the upper portion of said reactor vessel andterminating within said vapor cooling vessel adapted for the passage ofhigh temperature hydrocarbon vapors therebetween, concentric heatingelements disposed about said gas impervious conduit to maintain theinterior surface temperature thereof above the dew point of said hightemperature hydrocarbon vapors, a cylindrical concentric baflle in saidvapor cooling vessel about said gas impervious cylindrical conduit andsaid concentric heating elements radially spaced therefrom to form anannular passageway, said passageway opening into said vapor coolingvessel at the terminus of said gas impervious cylindrical conduit,conduit means for injecting a bleed gas into said annular passageway,means in said vapor cooling vessel for dispersing a liquid coolant inthe hydrocarbon vapors issuing from said gas impervious cylindricalconduit, and conduit means for withdrawing cooled vapors and liquid fromsaid vapor cooling vessel.

References Cited in the file of this patent UNITED STATES PATENTS-l,892,440 Frankenberg Dec. 27, 1932 2,100,758 Ackeren Nov. 30, 19372,391,818 Brandt Dec. 25, 1945 2,557,971 Jacklin June 26, 1951 2,608,527Holland Aug. 26, 1952 2,719,114 Lefier Sept. 27, 1955

1. IN A HYDROCARBON OIL FLUID COKING PROCESS WHEREIN HIGH TEMPERATUREHYDROCARBON VAPORS ARE PRODUCED IN A COKING ZONE AND SAID HYDROCARBONVAPORS HAVE A PROPENSITY TO FORM COKE DEPOSITS ON ATTENDANT SURFACE, AMETHOD OF PREVENTING SAID COKE DEPOSITS WHILE COOLING SAID HYDROCARBONVAPORS THROUGH A CRITICAL COKE DEPOSITION TEMPERATURE RANGE WHICHCOMPRISES WITHDRAWING SAID HYDROCARBON VAPORS FROM SAID COKING ZONETHROUGH A GAS IMPERVIOS PASSAGEWAY, MAINTAINING THE INTERIOR SURFACETEMPERATURE OF SAID PASSAGEWAY ABOVE THE DEW POINT OF SAID HYDROCARBONVAPORS BY MEANS O F HEATING ELEMENTS, INJECTING SAID HYDROCARBON VAPORSFROM SAID PASSAGEWAY INTO A GAS COOLING ZONE AT AN INTERIOR POINTREMOVED FROM THE CONFINES OF SAID GAS COOLING ZONE, FORMING A SECONDPASSAGEWAY IN SAID COOLING ZONE ABOUT SAID GAS IMPERVIOUS PASSAGEWAY ANDHEATING ELEMENTS EXTENDING INTO SAID COOLING ZONE, SAID SECONDPASSAGEWAY TERMINATING AND OPENING INTO SAID GAS COOLING ZONE AT THEPOINT OF TERMINATION OF SAID GAS IMPERVIOUS PASSAGEWAY, MAINTAINING THEOUTER CONFINES OF SAID PASSAGEWAY BELO 780*F., INJECTING A BLEED GASINTO SAID SECOND PASSAGEWAY TO PREVENT ENTRANCE OF HYDROCARBON VAPORSTHERETO, COOLING SAID VAPORS BELOW 780*F. IN THE VAPORS PHASE THROUGHCONTACT WITH A FINELY DIVIDED LIQUID COOLANT, AND WITHDRAWING COOLEDVAPORS FROM SAID COOLING ZONE.